Molecular assembly synthesis of microporous FeN4-doped carbon plates implanted with Fe3C-doped graphitized carbon nanobelts for efficient oxygen reduction

Abstract

Transition metal/nitrogen-doped carbon materials combining the merits of high surface, high graphitization, 2D morphology and rich active sites are appealing for electrocatalytic oxygen reduction reaction (ORR). This work proposes a molecular assembly strategy to synthesize novel Fe/N-doped carbon materials with these properties acquired simultaneously. Histidine (His), potassium bicarbonate (PBC) and ferrous bisglycinate (Fe(Gly)₂) are assembled into a uniformly mixed aggregate. Pyrolysis of the aggregate converts the His component to 2D highly microporous carbon plates carrying atomic FeN₄ sites via foaming, carbonization and in-situ activation and drives the Fe(Gly)₂ component to form highly graphitized carbon nanobelts encapsulating Fe₃C nanoparticles via carbonization and local catalytic graphitization. The typical material possesses a high surface area of 1728 m² g⁻¹, uniform micropores of 0.6 and 1.8 nm and rich FeN₄ sites and Fe₃C nanoparticles. It shows high ORR performance with a half-wave potential of 0.90 V, fast kinetics, low H₂O₂ yields, high stability and superior methanol tolerance. The influences of the Fe(Gly)₂ dosage and pyrolysis temperature and the roles of Fe(Gly)₂ and PBC are discussed. The high ORR performance of the typical material originates from the active FeN₄ and Fe₃C sites and the high porosity and graphitization for facile mass and electron transfer.